calcfig
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Is It Worth Replacing Halogen Bulbs with LED?

Swapping twelve 50 W halogen bulbs for 7 W LEDs, used 3 hours a day, saves about $102.61 a year at 18.16 cents per kWh. At $4 a bulb ($48 in all) that pays back in about 5.6 months.

Try your own numbers

W

On the label or the bulb. Example values: a 50 W halogen and a 7 W LED.

W
h
$

Your own price. The starting figure is only a placeholder.

¢/kWh

Change the area above or type your own rate from your bill.

Saving per year$102.61
Payback5.6 months
Energy saved per year565 kWh
Net after 10 years$978.08

12 × (50 W − 7 W) × 3 h × 365 days ÷ 1,000 = 565 kWh a year. × 18.16¢/kWh = $102.61 a year. $48.00 ÷ $102.61 = 5.6 months.

Ignores price changes, bulb or appliance life and the time value of money. Heat from the old item may have been useful in winter.

Fig. 1 Twelve bulbs, 50 W to 7 W, 3 hours a day.

Every formula is tested against worked examples. How we check

Hours a daySaving per yearPayback
1 h$34.201.4 years
2 h$68.418.4 months
3 h$102.615.6 months
4 h$136.814.2 months
8 h$273.622.1 months

Fig. 2 The same upgrade used for more or fewer hours.

Last checked 11/10/2026. Sources: U.S. Energy Information Administration: Electric Power Monthly, Table 5.6.A.

How the saving is worked out

Each bulb saves 50 − 7 = 43 W. Twelve bulbs for 3 hours on 365 days is 12 × 43 × 3 × 365 ÷ 1,000 = 565 kWh a year. At 18.16 cents per kWh that is $102.61 a year. The bulbs cost $48, so $48 ÷ $102.61 is 0.47 of a year, or 5.6 months. Over ten years the net gain is $978.08, before allowing for bulbs that would need replacing anyway.

What is assumed. The rate is the US average residential price from the EIA, not your own. Halogens are assumed to be 50 W and LEDs 7 W with similar brightness. The wattages and the price of the new item are examples. Use the figures on your own bulbs, appliance label and receipt.

When the answer changes

Fewer hours make the payback longer in proportion: at 1 hour a day the same swap takes about 17 months. A lamp used for 10 minutes a night may never repay the bulb through energy alone, though LEDs also last far longer than halogens.

Common questions

Do LEDs really save this much?

The arithmetic is exact for the wattages you enter. Check the watts printed on your current bulbs and on the LED pack, because they vary.

Is there a catch with dimmers?

Some older dimmers do not suit LEDs. Check the pack, because the cost of a new dimmer would add to the up-front cost you enter.

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